Sabine measured absorption as equivalent open-window area, verified experimentally

Evidence

For example, a large area of a material with a low value of absorption coefficient may well have more influence than a small area of material with more absorption. In the Sabine equation, this is easily done by multiplying the absorption coefficient of the material by its total area and then adding up the contributions from all the surfaces in the room. This resulted in a figure Sabine called the “equivalent open window area,” as he assumed and experimentally verified that the absorption coefficient of an open window was equal to 1. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2845

Categorization

• DEFINE: Explains the ‘equivalent open window area’ concept — an open window absorbs all incident sound, giving a coefficient of 1.
• XREF: Sabine is the founding figure of architectural acoustics; this is the historical lineage the reader wants to follow.